The Ohio Democrat. (Logan, O. [Ohio]) 1886-1906, 1887-09-10
GATHERING THE GOLD.
Methods Adopted for Gctting tho Met
Out OF tile Free Milling Ore.


Methods Adopted for uctting tho Metal
Out OF the Free Milling Orc.
At Breckenridge, Col, tho other day,
] saw the Jumbo stamp-mill, and there
got fair insight into the method of
getting the gold out of what Is called
free milling ore. The stuff that comes
from the mine is first put through
crusher. which breaks It up fine, and
the product is then run through rollers
which pulverizes it, though, perhaps.
coarsely. From the rollers it falls to
the lower floor, upon which the NOR
tars are located. At the Jumbo mill
the dirt is fed to the stamps by hand;
In other mills it falls through chutes
which work automatically, and never
feed more than is necessary at n
time. The stamps are arranged in
batteries of five stamps each. They
work up and down in oak easements,
and their motions are regulated by
cams on shaft gearcd to the motive
machinery. The stamps weigh from
450 to 300 pounds, according to tho
character of the ore treated. Water
flows into the mortars and out OF them
down tables to the waste fumes which
carry the refuse away. Stamps in this
country run us low as thirty drops u
minute. and seldom over sixty; in
California they drop seventy to 100
times minute. The two kinds of mills
are distinguished by the rapidity or
slowness of their drops, and those used
here are all built by Peter Mcfarland,
and are called Gilpin County mills,
from McFarland's home place, which
is in Gilpin County, while the others
are known as California mills. They
cost from $3.50 for tive-stamp pros
pecting mill to S5O,0OO for 100-stamp
mill. The dirt being fed into the mortars
is pounded and pounded by the stamps;
the silica, porphyry and other refuse
is carried off by the water. but the gold
is caught by two copper plates coated
with quicksilver that line the sides of
the mortar; any of the precious metal
that escapes from the mortar may be
caught on the 4x8 feet copper plates
that are quicksilver coated and lie on
the table over which the refuse is car
ried. Some of the gold gets away, OF
course, but the Jumbo saves as much
as 80 per cent. of its gold, and McFar-
land is now building mills which he
claims will save 95 per cent. of the as
sayed value of ore.
Concentrators are used where the ore
is too low grade to pay for smelling in
its crude state. BY concentrating SIC
or S12 ore may be handled so that the
mill product, which will represent six
or seven tons in ore, may be worth SIC
to $50 per ton. The scheme is very
simple. The csushcd and rolled orc is
fed through chutes to revolving screens
ranging in size from threc-fourths incl
openings to one-eighth. Each OF these
screens has trough and chute which
feeds u Jig box. The Jig boxes work OF
an eccentric and keep up spasm-likt
motion. There is Il screen in each about
six inches from the top, and this screcl
is covered with lead or other heavy
ore material. which prevents thu
silica, porphyry and other light stuf
from going through. The motion
shakes the metal to the bottom of th'
boxes, where it remains until valves il
the bottom are opened and the concen
trates are removed. This machine, iik'
all the others called by different names
and known as triumps, frue vanners
buddles, bump plates. etc, is an appli
cation of the well-known law of specific
gravity; the heaviest material falls tt
the bottom in all these machines, an(
the light stuff goes dancing away OF
the water. The bump plate, which il
claimetfio be new invention by Pete
Mcfarland, is u large steel plate set n
an incline of few degrees; the ore il
fed to the lower part of the place from
Il water trough. and as the high en'
bumps it carries forward and up owe
the top of the plate the heavy concen
trates.-COr. st. Louis Globe Democrat